Energy Storage Device

The present invention relates to an energy storage device that includes an electrode assembly.

Conventionally, there has been known an energy storage device in which a pair of terminals (a negative electrode output terminal and a positive electrode terminal) is mounted on a lid body (lid) of a container which accommodates an electrode assembly in a state where the pair of terminals protrudes (see, for example, Patent Document 1).

Patent Document 1: JP-A-2010-73580

In recent years, an energy storage device is required to be capable of storing a larger electrode assembly by using a container that has a longer length between terminals. In such an energy storage device, a pair of terminals protrudes from a lid body. As a result, in a case where a pair of terminals protrude from a lid body so that a distance between the terminals of the container is elongated, a surplus space formed between the terminals outside the container also becomes large. In order to suppress the surplus space outside the container from becoming large, it may be considered that the energy storage device adopts a configuration where a recessed portion for accommodating terminals is formed on the container. However, in a case where a surplus space is formed in the container attributed to such a recessed portion, as a result, there is a concern that space utilization efficiency of the energy storage device is reduced.

It is an object of the present invention to suppress the lowering of space utilization efficiency of an energy storage device.

To achieve the above-mentioned object, according to one aspect of the present invention, there is provided an energy storage device that includes: an electrode assembly that is formed by stacking a plurality of plates and is elongated in a predetermined direction intersecting with a stacking direction; a container that accommodates the electrode assembly; and a terminal that is electrically connected to the electrode assembly, in which the electrode assembly includes: an electrode assembly body; and a connecting portion that protrudes from an end portion of the electrode assembly body in the predetermined direction, the terminal includes a terminal body portion that protrudes from a terminal mounting surface of the container in a direction intersecting with the stacking direction, and a distal end portion of the electrode assembly body in a protruding direction of the terminal body portion protrudes with respect to the terminal mounting surface.

According to the present invention, it is possible to suppress the lowering of the space utilization efficiency of an energy storage device.

According to the energy storage device of one aspect of the present invention, the distal end portion of the terminal body portion of the electrode assembly body in a protruding direction protrudes with respect to the terminal mounting surface of the container and hence, the electrode assembly body can be disposed in the surplus space formed between the terminal body portions of the pair of terminals. With such a configuration, the surplus space in the container can be reduced. Accordingly, it is possible to suppress the lowering of the space utilization efficiency of the energy storage device.

According to the energy storage device described in the above-mentioned (2), the distal end portion of the electrode assembly body protrudes more than the distal end portions of the terminal body portions. Accordingly, the electrode assembly body can be disposed with a larger size in the surplus space formed between the terminal body portions of the pair of terminals. Accordingly, it is possible to suppress the lowering of the space utilization efficiency of the energy storage device.

According to the energy storage device described in (3), the current collector extends in the direction intersecting with the protruding direction of the connecting portion in the space that overlaps with the terminal mounting surface and hence, the current collector does not protrude from the space. That is, the current collector and the connecting portion are joined in the space and hence, the joining structure of these constitutional elements does not protrude from the space. With such a configuration, the electrode assembly body can be disposed as large as possible and hence, an electric capacitance can be further increased.

According to the energy storage device described in the above-mentioned (4), the second joint portion is bent with respect to the first joint portion in a direction away from the electrode assembly body and hence, the second joint portion can be easily joined to the terminal disposed more outside than the electrode assembly body.

In the energy storage device described in the above (5), the length of the terminal body portion in the stacking direction is longer than the length of the terminal body portion in the predetermined direction. Accordingly, it is possible to form the terminal body portion as large as possible in the terminal mounting surface while suppressing the increase in size of the container in the predetermined direction. With such a configuration, a joint area between the conductive member such as a bus bar and the terminal body portion can be made as large as possible.

According to the energy storage device described in the above-mentioned (6), the connecting portion is disposed in the space that overlaps with the terminal mounting surface when the terminal mounting surface is viewed in the plan view and hence, the electrode assembly body can be formed as large as possible. The electrode assembly body is a portion that contributes to the storage of energy (the generation of power) and hence, if the portion can be formed with a large size, the electric capacitance can be increased.

To achieve the above-mentioned object, according to another aspect of the present invention, there is provided an energy storage device that includes: an electrode assembly that is formed by stacking a plurality of plates and is elongated in a predetermined direction intersecting with a stacking direction; a container that accommodates the electrode assembly; and a pair of terminals that is electrically connected to the electrode assembly, in which the electrode assembly includes: an electrode assembly body; and a pair of connecting portions that protrudes from both end portions of the electrode assembly body in the predetermined direction, the pair of terminals is disposed at positions where the pair of terminals interpose the electrode assembly body in the predetermined direction, at least one terminal out of the pair of terminals includes a terminal body portion that protrudes from a terminal mounting surface in the container in a direction intersecting with the stacking direction, and a distal end portion of the electrode assembly body in a protruding direction of the terminal body portion is coplanar with the terminal mounting surface or protrudes with respect to the terminal mounting surface.

According to the energy storage device of another aspect of the present invention, the distal end portion of the terminal body portion of the electrode assembly body in the protruding direction is coplanar with the terminal mounting surface of the container or protrudes with respect to the terminal mounting surface of the container. Accordingly, the electrode assembly body can be disposed in the surplus space formed between the terminal body portions of the pair of terminals. With such a configuration, the surplus space in the container can be reduced. Accordingly, it is possible to suppress the lowering of the space utilization efficiency of the energy storage device.

Hereinafter, energy storage devices according to the embodiments (including modifications of the embodiments) of the present invention are described with reference to the drawings. All embodiments described hereinafter are comprehensive examples or specific examples. Numerical values, shapes, materials, constitutional elements, arrangement positions and connection modes of the constitutional elements, manufacturing steps, the order of the manufacturing steps, and the like in the following exemplary embodiment are provided as examples, and are not intended to limit the present invention. In the respective drawings, sizes and the like are not strictly illustrated. In the respective drawings, identical or substantially identical constitutional elements are given the same symbols.

In the following description and drawings, a direction extending along a winding axis of an electrode assembly, a direction along which the electrode assembly extends, or a direction that a pair of short-side surfaces of a container faces each other is defined as an X-axis direction. A direction along which a pair of long-side surfaces of the container faces each other or a thickness direction of the container is defined as a Y-axis direction. A direction along which a bottom surface of a container body of the container and a top surface of a lid body are arranged or a vertical direction is defined as a Z-axis direction. The X-axis direction is an example of a predetermined direction. These X-axis direction, Y-axis direction, and Z-axis direction are the directions that intersect with each other (orthogonal to each other in the present embodiments). A configuration is also considered where the Z-axis direction is not the vertical direction depending on a use mode. However, in the description made hereinafter, for the sake of convenience of the description, the description is made by assuming the Z-axis direction as the vertical direction.

In the description made hereinafter, an X-axis positive direction indicates an arrow direction of an X-axis, and an X-axis negative direction indicates a direction opposite to the X-axis positive direction. The same goes for the Y-axis direction and the Z-axis direction. Expressions indicating the relative directions or the relative postures such as “parallel” or “orthogonal” also include cases where such directions or postures are not taken in a strict meaning of the terms. For example, a state where two directions are orthogonal to each other means not only a state where these two directions are completely orthogonal to each other but also a state where these two directions are substantially orthogonal to each other, that is, for example, a state where these two directions are orthogonal to each other with slight deviation of approximately several percent.

First, the overall configuration of an energy storage deviceaccording to the embodiment will be described with reference toand.is a perspective view illustrating an external appearance of the energy storage deviceaccording to the embodiment.is an exploded perspective view of the energy storage deviceaccording to the embodiment illustrating respective constitutional elements when the energy storage deviceis disassembled.

The energy storage deviceis an energy storage device into which electricity can be charged from the outside and from which electricity can be discharged to the outside. In this embodiment, the energy storage devicehas an approximately rectangular parallelepiped shape. For example, the energy storage deviceis a battery used in an electricity storage application, a power source application, or the like. Specifically, the energy storage deviceis used as a battery or the like for driving a mobile body such as an automobile, a motorcycle, a watercraft, a ship, a snowmobile, an agriculture machine, a construction machine, or a railway vehicle for an electric railway, or is used as a battery for starting an engine of the mobile body. As the above-described automobile, an electric vehicle (EV), a hybrid electric vehicle (HEV), a plug-in hybrid electric vehicle (PHEV), and an automobile that uses a fossils fuel (a gasoline, a light oil, a liquefied natural gas or the like) are exemplified. As an example of the railway vehicle for the electric railway described above, a train, a monorail, a linear motor car, and a hybrid train including both a diesel engine and an electric motor are exemplified. The energy storage devicecan also be used as a stationary battery or the like used as a home-use battery, a business-use battery, or the like.

The energy storage deviceis not limited to a non-aqueous electrolyte secondary battery. The energy storage devicemay be a secondary battery other than the non-aqueous electrolyte secondary battery, or may be a capacitor. The energy storage deviceis not necessarily a secondary battery, and may be a primary battery that allows a user to use stored electricity even when the user does not charge the energy storage device. The energy storage devicemay be a battery that uses a solid electrolyte. The energy storage devicemay be a pouch-type energy storage device. In the present embodiment, the energy storage devicethat uses a flat rectangular parallelepiped shape as the reference is illustrated. However, the shape of the energy storage device, that is, the shape of the containeris not limited to a shape that is formed using a rectangular parallelepiped shape as the reference, and may be a shape that is formed using a polygonal columnar shape, an elongated circular columnar shape, an elliptical columnar shape, a circular columnar shape or the like other than the rectangular parallelepiped shape as the reference.

As illustrated inand, the energy storage deviceincludes: a container; a pair of electrode terminals, and a pair of outer gaskets. A pair of inner gaskets, a pair of current collectors, and an electrode assemblyare accommodated in the container. Specifically, respective members (the electrode terminal, the outer gasket, an inner gasket, a current collectorand the like, the same understanding being adopted in the description made hereinafter) of a positive electrode are disposed on one end portion of the containerin the X-axis positive direction. The respective members of a negative electrode are disposed at the other end portion of the containerin the X-axis negative direction. To be further more specific, on a first side surface portionof the containerin the X-axis positive direction, the respective members of the positive electrode are disposed at an end portion in the Z-axis positive direction. That is, the first side surface portionis a range where the respective members of the positive electrode are disposed from an end surface of the containerin the X-axis positive direction. For example, the first side surface portionis a portion within a range of 1% to 10% of the length of the containerfrom the end surface of the containerin the X-axis positive direction with respect to the X-axis direction.

On a second side surface portionof the containerin the X-axis negative direction, the respective members of the negative electrode are disposed at an end portion in the Z-axis positive direction. That is, the second side surface portionis a range in which the respective members of the negative electrode are disposed from an end surface of the containerin the X-axis negative direction. For example, the second side surface portionis a portion within a range of 1% to 10% of the length of the containerfrom the end surface of the containerin the X-axis negative direction with respect to the X-axis direction.

Although an electrolytic solution (a non-aqueous electrolyte) is sealed in the container, the illustration of the electrolytic solution is omitted. A kind of the electrolyte solution is not particularly limited provided that the performance of the energy storage deviceis not impaired, and various kinds of electrolyte solutions can be selected. Besides the constituent elements described above, the energy storage devicemay further include: spacers that are disposed on the sides of the electrode assembly, above the electrode assembly, or below the electrode assembly; an insulating film that wraps the electrode assembly; and the like.

The containeris a case having a profile (a substantially rectangular parallelepiped shape) using a flat rectangular parallelepiped shape that is elongated in the X-axis direction as the reference. For example, a length of the containerin the X-axis direction is set 3 times or more as long as a length of the containerin the Z-axis direction. In, the rectangular parallelepiped shape that is used as the reference is indicated by a double-dashed chain line L. Specifically, the containerhas the profile where a cutout having a rectangular shape is formed at upper portions of both end portions in the X-axis direction of the flat rectangular parallelepiped shape elongated in the X-axis direction. It may be also expressed that each cutout forms a recessed portionas viewed in view of the rectangular parallelepiped shape used as the reference. That is, the recessed portionis formed on each of the first side surface portionand the second side surface portionof the containerat the end portion in the Z-axis positive direction. Further, the electrode terminalis disposed in the recessed portion. With such a configuration, in each of the first side surface portionand the second side surface portionof the container, the recessed portionand (the entirety of) the electrode terminalin the recessed portionoverlap with each other in the Z-axis direction.

is an explanatory view illustrating rough positions of the first side surface portion, a second side surface portion, and the recessed portionsaccording to the embodiment. In, the first side surface portionand the second side surface portionare surrounded by a broken line, and the recessed portionsare surrounded by a dotted chain line.

As illustrated inand, specifically, the first side surface portionincludes a first upper side surface, a first upper surface, and a first side surface. The first side surface portionis elongated in the Z-axis direction as viewed in the X-axis direction. The first upper side surfaceis disposed at an upper portion of the first side surface portion, and is a rectangular flat surface that is parallel to a YZ plane and is elongated in the Z-axis direction. The first upper surfaceis a flat surface extending in the X-axis positive direction from a lower end of the first upper side surface, and is a rectangular flat surface that is parallel to the XY plane and is elongated in the X-axis direction. The first side surfaceis a flat surface extending downward from an end portion of the first upper surfacein the X-axis positive direction, and is a rectangular flat surface that is parallel to the YZ plane and is elongated in the Z-axis direction. In this manner, the recessed portionof the first side surface portionis defined by the first upper side surfaceand the first upper surface, and an end portion of the recessed portionin the Z-axis positive direction and an end portion of the recessed portionin the X-axis positive direction are opened. Accordingly, the end portion of the first side surface portionin the Z-axis positive direction (a corner portion of the containerin the X-axis positive direction and in the Z-axis positive direction) is formed in a shape where surfaces extending in the X-axis direction and the Z-axis direction are recessed and the shape penetrates in the Y-axis direction. In other words, the recessed portionof the first side surface portionis a recessed portion where a corner portion of the containerin the X-axis positive direction and in the Z-axis positive direction is recessed (cutted out) in a quadrangular shape (L shape) as viewed in the Y-axis direction.

The second side surface portionincludes a second upper side surface, a second upper surface, and a second side surface. The second side surface portionis elongated in the Z-axis direction as viewed in the X-axis direction. The second upper side surfaceis disposed at an upper portion of the second side surface portion, and the second upper side surfaceis a rectangular flat surface that is parallel to the YZ plane and is elongated in the Z-axis direction. The second upper surfaceis a flat surface extending in the X-axis negative direction from a lower end of the second upper side surface, and the second upper surfaceis a rectangular flat surface that is parallel to the XY plane and is elongated in the X-axis direction. The second side surfaceis a flat surface extending downward from an end portion of the second upper surfacein the X-axis negative direction, and the second side surfaceis a rectangular flat surface that is parallel to the YZ plane and is elongated in the Z-axis direction. In this manner, the recessed portionof the second side surface portionis defined by the second upper side surfaceand the second upper surface, and an end portion of the recessed portionin the Z-axis positive direction and an end portion of the recessed portionin the X-axis negative direction are opened. Accordingly, the end portion of the second side surface portionin the Z-axis positive direction (a corner portion of the containerin the X-axis negative direction and in the Z-axis positive direction) is formed in a shape where surfaces extending in the X-axis direction and the Z-axis direction are recessed and the shape penetrates in the Y-axis direction. In other words, the recessed portionof the second side surface portionis a recessed portion where a corner portion of the containerin the X-axis negative direction and in the Z-axis positive direction is recessed (cutted out) in a quadrangular shape (L shape) as viewed in the Y-axis direction.

In the container, both end surfaces that face each other in the Y-axis direction each form the long side surfaces. Each long side surfaceis a flat surface that is parallel to the XZ plane and is elongated in the X-axis direction, and both end portions of the long side surfacein the X-axis direction have shapes corresponding to the first side surface portionand the second side surface portion.

With respect to both end surfaces of the containerthat face each other in the Z-axis direction, the end surface in the Z-axis positive direction is a top surface, and the end surface in the Z-axis negative direction is a bottom surface. The top surfaceis a rectangular flat surface that is parallel to the XY plane and is elongated in the X-axis direction. The top surfaceconnects an upper end of the first upper side surfaceof the first side surface portionand an upper end of the second upper side surfaceof the second side surface portion. The bottom surfaceis a rectangular flat surface that is parallel to the XY plane and is elongated in the X-axis direction. The bottom surfaceconnects the lower end of the first side surfaceof the first side surface portionand the lower end of the second side surfaceof the second side surface portion.

The containerincludes a container bodyand a lid body, and is formed in a substantially rectangular parallelepiped shape by assembling the container bodyand the lid body. The container bodyhas a pair of long side surfacesand the bottom surface. The lid bodyhas the first upper side surface, the first upper surface, the first side surface, the second upper side surface, the second upper surface, the second side surface, and the top surface.

Specifically, the container bodyis a substantially U-shaped sheet metal with an upper side thereof opened as viewed in the X-axis direction. The container bodyhas flat plate-shaped long side wall portions that form a pair of the long side surfacesat both end portions thereof in the Y-axis direction. The container bodyhas a flat plate-shaped rectangular bottom wall portion that forms the bottom surfaceat an end portion in the Z-axis negative direction.

The lid bodyis a sheet metal with a lower side thereof opened as viewed in the Y-axis direction. The lid bodyhas a bent plate portion that forms the first upper side surface, the first upper surface, and the first side surfaceat an end portion in the X-axis positive direction. The lid bodyhas a bent plate portion that forms the second upper side surface, the second upper surface, and the second side surfaceat an end portion in the X-axis negative direction. The lid bodyhas a flat plate-shaped and rectangular top wall portion that forms the top surfaceat an end portion in the Z-axis positive direction.

With such a configuration, the containerhas the structure where the inside of the containeris sealed. Such sealed structure is obtained by housing the electrode assemblyand the like in the container bodyand, thereafter, by joining the container bodyand the lid bodyto each other by welding or the like. A material of the container(the container bodyand the lid body) is not particularly limited. However, for example, it is preferable that the containerbe made of weldable metal such as stainless steel, aluminum, an aluminum alloy, iron, or a plated steel plate.

Although not illustrated in the drawings in this embodiment, a solution filling portion and a gas release valve are formed on the lid body. The gas release valve is a safety valve that releases a pressure in the containerwhen such a pressure is excessively increased. The solution filling portion is a portion for filling an electrolyte solution into the containerat the time of manufacturing the energy storage device.

The electrode terminalsare terminals (a positive electrode terminaland a negative electrode terminal) that are electrically connected to the electrode assemblyvia the current collectors. That is, the electrode terminalsare members that are made of metal and are provided for discharging electricity stored in the electrode assemblyto a space outside the energy storage device, and for charging electricity into an inner space in the energy storage deviceto store electricity in the electrode assembly. Although a material of the electrode terminalis not particularly limited, for example, the electrode terminals(the positive electrode terminaland the negative electrode terminal) are respectively formed of a conductive member made of aluminum, an aluminum alloy, copper, a copper alloy or the like. The electrode terminalsare connected (joined) to the current collectorsby caulking, welding or the like, and are mounted on the lid body.

In the present embodiment, the electrode terminalincludes a terminal body portionand a shaft portionthat protrudes from the terminal body portion. The electrode terminalmay be a bolt terminal having a bolt portion that protrudes in the Z-axis direction and on which a male screw portion is formed. The terminal body portionis a portion that protrudes outward from a terminal mounting surface of the container. The terminal mounting surface is formed of the first upper surfaceor the second upper surface. At any terminal mounting surface, the terminal body portionprotrudes outward from the containeralong the Z-axis direction. Through holesthrough which a shaft portionpasses are formed in the lid bodyat positions that correspond to the respective terminal mounting surfaces. The shaft portionis connected (joined) to the current collectorby caulking in a state where the shaft portionpenetrates the terminal mounting surface, the outer gasket, the inner gasketand the current collector. The positional relationship between the terminal body portionsand the respective recessed portionsafter joining will be described later.

The current collectorsare current collecting members (a positive electrode current collectorand a negative electrode current collector) having conductivity. The current collectorsare provided such that one current collectoris disposed on each of both sides of the electrode assemblyin the X-axis direction. The current collectorsare connected (joined) to the electrode assemblyand the electrode terminalsso as to electrically connect the electrode assemblyand the electrode terminalsto each other. Specifically, the current collectoris an integral body formed of: a first joint portionthat is connected (joined) to a connecting portionof the electrode assemblydescribed later by welding, caulking or the like; and a second joint portionthat is connected (joined) to the electrode terminalby caulking, welding or the like and is connected to the lid bodyas described above. The first joint portionand the second joint portionare each a flat plate-like portion. The first joint portionand the second joint portionare formed by bending one sheet metal. The details of the current collectorwill be described later.

Although a material of the current collectoris not particularly limited, for example, the positive electrode current collectoris formed of a conductive member made of aluminum or an aluminum alloy or the like in the same manner as a positive electrode substrateof the electrode assemblydescribed later, and the negative electrode current collectoris formed of a conductive member made of copper or a copper alloy or the like in the same manner as a negative electrode substrateof the electrode assemblydescribed later.

The outer gasketis a plate-like rectangular sealing member having insulating property that is disposed between the lid bodyof the containerand the electrode terminal. The outer gasketprovides insulation and sealing between the lid bodyand the electrode terminal. The inner gasketis a plate-like rectangular sealing member having insulating property that is disposed between the lid bodyand the current collector. The inner gasketprovides insulation and sealing between the lid bodyand the current collector. The outer gasketand the inner gasketare made of a resin or the like having an electrically insulating material such as polypropylene (PP), polyethylene (PE), polystyrene (PS), a polyphenylene sulfide resin (PPS), polyphenylene ether (PPE (including modified PPE)), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polyether ether ketone (PEEK), tetrafluoroethylene/perfluoroalkyl vinyl ether (PFA), polytetrafluoroethylene (PTFE), polyether sulfone (PES), an ABS resin, or a composite material of the above-described materials.

The electrode assemblyis an energy storage element (a power generating element) that is formed by winding plates and can store electricity. The electrode assemblyhas an elongated shape extending in the X-axis direction, and has an elongated circular shape as viewed in the X-axis direction. The electrode assemblyhas a shape where a length in the X-axis direction is, for example, 300 mm or more, and more specifically, about 500 mm to 1500 mm. With such a configuration, the length of the electrode assemblyin the X-axis direction is set longer than the length of the electrode assemblyin the Z-axis direction. For example, the length of the electrode assemblyin the X-axis direction istimes or more as large as the length of the electrode assemblyin the Z-axis direction. The electrode assemblyincludes: a body portion (electrode assembly body); and a pair of connecting portionsthat protrudes from both end portions of the body portion. As described above, the connecting portionsare connected (joined) to the current collectors.

Specifically, the plurality of connecting portionsprotrude from an intermediate portion in the Z-axis direction at both end portions of the body portionin the X-axis direction. For example, a positive electrode connecting portionis disposed at the intermediate portion in the Z-axis direction at one end surface of the body portionin the X-axis positive direction, and the negative electrode connecting portionis disposed at the intermediate portion in the Z-axis direction at the other end surface of the body portionin the X-axis negative direction. The configuration of such an electrode assemblywill be described in detail hereinafter.

is a perspective view illustrating the configuration of the electrode assemblyaccording to the embodiment. Specifically,illustrates the configuration of the winding state of the plates in the electrode assemblyin a state where the winding state of the plates is partially developed. As illustrated in, the electrode assemblyincludes a positive plate, a negative plate, and separators,.

The positive plateis a plate (an electrode plate) that is formed such that a positive active material layeris formed on a surface of the positive electrode substratethat is an elongated strip-shaped metal foil made of aluminum or an aluminum alloy. The negative plateis a plate (an electrode plate) that is formed such that a negative active material layeris formed on a surface of the negative electrode substratethat is an elongated strip-shaped metal foil made of copper or a copper alloy. As materials for forming the positive electrode substrateand the negative electrode substrate, known materials such as nickel, iron, stainless steel, titanium, fired carbon, a conductive polymer, a conductive glass, and an Al—Cd alloy can be appropriately used provided that the materials are stable to an oxidation-reduction reaction during charging and discharging. As a positive active material used for forming the positive active material layerand a negative active material used for forming the negative active material layer, known materials can be appropriately used provided that the materials are a positive active material and a negative active material capable of occluding and discharging lithium ions.

For example, as the positive active material, a polyanion compound such as LiMPO, LiMSiO, or LiMBO(M representing one kind or two or more kinds of transition metal elements selected from Fe, Ni, Mn, Co, and the like), lithium titanate, a spinel-type lithium manganese oxide such as LiMnOor LiMmNiO, a lithium transition metal oxide such as LiMO(M representing one kind or two or more kinds of transition metal elements selected from Fe, Ni, Mn, Co, and the like), or the like can be used. As the negative active material, besides lithium metal and a lithium alloy (lithium metal-containing alloys such as lithium-silicon, lithium-aluminum, lithium-lead, lithium-tin, lithium-aluminum-tin, lithium-gallium, and a wood's alloy), an alloy capable of occluding and releasing lithium, a carbon material (for example, graphite, non-graphitizable carbon, graphitizable carbon, low-temperature calcined carbon, amorphous carbon, and the like), a silicon oxide, a metal oxide, a lithium metal oxide (LiTiOor the like), a polyphosphoric acid compound, and a compound of transition metal and an element belong to any one of groups 14 to 16, such as CoOor FeP, that is generally referred to as a conversion negative electrode can be named.

The separators,are each formed of a microporous sheet made of a resin. As a material of the separatorsand, a known material can be appropriately used provided that the performance of the energy storage deviceis not impaired. For example, as the separatorsand, a woven fabric that is insoluble in an organic solvent, a nonwoven fabric, a synthetic resin microporous membrane made of a polyolefin resin such as polyethylene, or the like can be used.

The electrode assemblyis formed by alternately stacking and winding the positive plate, the negative plate, and the separators,. That is, the electrode assemblyis formed by stacking and winding the negative plate, the separator, the positive plate, and the separatorin this order. In the present embodiment, the electrode assemblyis a winding-type electrode assembly formed by winding the positive plate, the negative plateand the like around the winding axis L extending in the X-axis direction. The winding axis L is a virtual axis that becomes a central axis when the positive plate, the negative plateand the like are wound, and in the present embodiment, the winding axis L is a straight line which passes through the center of the electrode assemblyand is parallel to the X-axis direction.

On the one end edge (end edge in the X-axis positive direction) of the positive platein the winding axis direction, a plurality of protruding membersthat protrude outward are disposed at a predetermined interval. In the same manner, on the other end edge (end edge in the X-axis negative direction) of the negative platein the winding axis direction, a plurality of protruding membersthat respectively protrude outward are disposed at a predetermined interval. Each of the protruding membersandis a portion where the active material layer containing the active material is not formed and the substrate layer is exposed (an active material layer-non-formed portion).

When the positive plate, the negative plate, and the separatorsandare wound, the protruding membersof the positive plateoverlap with each other on one end surface of the body portion, and the protruding membersof the negative plateoverlap with each other on the other end surface of the body portion. A portion where the protruding membersof the positive plateoverlap with each other forms the positive electrode connecting portion. That is, the positive electrode connecting portionis a portion that is formed by stacking a plurality of one members (protruding members) of the plate having the same polarity (the positive plates) out of the plurality of plates (the positive plateand the negative plate).